It may be desired to analyze a liquid not, or not only, for its bulk properties, but for the properties of its constituents, for example, properties of its ionic species. Therefore, the constituents have to be separated. It is known to do this by electrophoresis, including isotachophoresis, in which a sample of liquid is introduced into one end of a capillary tube and is subjected to an electric field. The sample, or constituents thereof, moves along the tube under the influence of the field, separating, for example into its various species, depending on their mobilities. Analysis can then be carried out on the individual species.
It is one object of the present invention to provide apparatus for and a method of separating liquid into its constituents in a particularly convenient manner.